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I'm an engineer with experience in applied cryptography, in particular in Smart Card systems.


Jun
26
comment Is it possible to get better randomness by using multiple PRNGs?
@Stephen Touset: that's true in an information-theoretic sense, and only with the critical assumption that the PRNGs are seeded from independent sources. However it is possible to devise (bad) PRNGs that individually have output in any particular run indistinguishable from random, but which XOR has horrible properties, even when both are seeded with true random. A trivial example is two identical CSPRNGs modified to entirely ignore their seed input; but it is possible to extend this to make the generators pass many, perhaps any fixed test.
Jun
26
revised Convert m-Sequence into a de Bruijn Sequence
x must be unsigned
Jun
26
revised Convert m-Sequence into a de Bruijn Sequence
Add softwware implementation
Jun
26
revised What are the methods to construct a primitive binary nonlinear feedback shift register (NLFSR)?
Move details to related answer
Jun
24
revised What are the methods to construct a primitive binary nonlinear feedback shift register (NLFSR)?
Give a NLFSR with period 2^n
Jun
24
comment Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
In an EMV context, yes $m\equiv n\equiv 0\pmod 8$ holds, because (for $m$) all messages are bytes, and (for $n$) public modulus has size multiple of 8 (and even 32, perhaps 64) by some (AFAIK unwritten) rule, as demonstrated (AFAIK, only) by the fact that EMV's ISO/IEC 9796-2 padding starts with '6A' (yes that's circular). However, $n\equiv 0\pmod 8$ does NOT hold in a PKCS#1 context. Messages with a number of bits not multiple of 8 are a rarity, but ISO/IEC 9796-2 also covers that.
Jun
24
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Improve description of ISO/IEC 9796-2 scheme 1 signature verification
Jun
24
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Polish
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Polish
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Polish
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Include a summary description of ISO/IEC 9796-2 scheme 1
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Also cite the best known attack on ISO/IEC 9796-2 scheme 1
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Indulge in self-citation
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Add parameters to the formal definition
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
More precise description of the restrictions of the definition given in EMV 4.3
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
The definition given is precisely the recognized one for total message recovery. Turned the update into an equally recognized definition of partial message recovery.
Jun
23
revised Functions that are only second-preimage resistant?
Minor notation fix
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Polish
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Polish
Jun
23
revised Description of signatures with message recovery (as in ISO/IEC 9796-2 and EMV Signatures)
Update with alternative definition